Electrode contacts

ABSTRACT

A device structure providing contact to conductive layers via a deep trench structure is disclosed. The device includes a first dielectric layer including a first opening. A first conductive layer is deposited over the first dielectric layer and the first opening. A second dielectric layer is deposited on the first conductive layer. The second dielectric layer includes a second opening. A second conductive layer is deposited over the second dielectric layer and the first and second openings. A semiconductor layer is deposited on the second dielectric layer such that the semiconductor layer is not continuous on at least part of the walls of the first or second openings. A top electrode layer is deposited on the semiconductor layer. The top electrode layer is in contact with the second conductive layer on at least part of the walls of the first or second openings.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Nos. 61/929,699, filed Jan. 21, 2014, and 61/920,732, filedDec. 25, 2013, each of which is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

In array devices with a common-electrode, the resistance of the commonelectrode can affect the quality of the device performance. In the caseof top emission displays, the top electrode needs to be transparent. Onemethod to fabricate a transparent electrode is to use very thinelectrodes. However, this results in higher resistivity which can be anissue for large area devices. In one method, the top electrode can becontacted to a conductive layer. However, developing a contact openingis very challenging since a shadow mask needs to be used to remove thesemiconductor layer from the opening.

Thus, there is a need of developing contact to conductive layers withoutusing a shadow mask for common-electrode devices. There is also a needto reduce the resistivity of an electrode to prevent a large voltagedrop in a device.

SUMMARY

According to one example, a device structure providing contact toconductive layers via a deep trench structure is disclosed. The devicestructure includes a first dielectric layer including a first opening.The first opening has walls on the first dielectric layer. A firstconductive layer is deposited over the first dielectric layer and thefirst opening. A second dielectric layer is deposited on the firstconductive layer. The second dielectric layer includes a second openinghaving walls on the second dielectric layer. A second conductive layeris deposited over the second dielectric layer and the first and secondopenings. A semiconductor layer is deposited on the second conductivelayer such that the semiconductor layer is not continuous on at leastpart of the walls of the first or second openings. A top electrode layeris deposited on the semiconductor layer. The top electrode layer is incontact with the second conductive layer on at least part of the wallsof the first or second openings.

Another example is a method of method of fabricating a device structureproviding contact to conductive layers via a deep trench structure. Themethod includes depositing a first dielectric layer and creating a firstopening in the first dielectric layer. The first opening has walls onthe first dielectric layer. A first conductive layer is deposited overthe first dielectric layer and the first opening. A second dielectriclayer is deposited on the first conductive layer. A second opening iscreated on the second dielectric layer. The second opening has walls onthe second dielectric layer. A second conductive layer is deposited overthe second dielectric layer and the first and second openings. Asemiconductor layer is deposited on the second conductive layer suchthat the semiconductor layer is not continuous on at least part of thewalls of the first or second opening. A top electrode layer is depositedon the semiconductor layer. The top electrode is in contact with thesecond conductive layer on at least part of the walls of the first orsecond opening.

Another example is a low resistance device including a backplane layerand a low resistance conductor layer having a pattern with a pluralityof edges on the backplane layer. A semiconductor layer is deposited onthe low resistance conductor layer. A high-resistance top conductorlayer is deposited on the semiconductor layer. The high-resistance topconductor layer is in contact with the low resistance conductor layer onat least one of the plurality of edges.

Another example is a method of forming a low resistance device. Themethod includes forming a backplane and depositing a low-resistanceconductive layer on the backplane. The low-resistance conductive layeris patterned to create a plurality of edges in the low-resistanceconductive layer. A semiconductor layer is deposited on the lowresistance conductor layer. A high-resistance top conductor layer isdeposited on the semiconductor layer. The high-resistance top conductorlayer is in contact with the low resistance conductor layer on at leastone of the plurality of edges.

Additional aspects of the invention will be apparent to those ofordinary skill in the art in view of the detailed description of variousembodiments, which is made with reference to the drawings, a briefdescription of which is provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings.

FIG. 1 is a cross-sectional view of a semiconductor device structurewith contacts to a common electrode.

FIGS. 2A-2G are diagrams showing the process of fabricating the devicestructure in FIG. 1;

FIG. 3 is a top plan view of the common electrodes in several of thedevices having a structure as shown in FIG. 1, showing the contact areasto the conductive layers in each device.

FIG. 4 is a sectional view of a crossing structure for improving theresistance of an electrode.

FIG. 5A is a side elevation of a crossing structure for improving theresistance with strip patterning.

FIG. 5B is a side elevation of another crossing structure for improvingthe resistance with mesh patterning.

While the invention is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. Itshould be understood, however, that the invention is not intended to belimited to the particular forms disclosed. Rather, the invention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1 is a cross-section view of an example structure to allowconnection of a top electrode to electrodes. The structure 100 in FIG. 1may be part of a semi-conductor device including transistors and othercomponents requiring electrical connection. The structure 100 includes afirst dielectric layer 102. A first conductive layer 104 is formed onthe first dielectric layer 102. A second dielectric layer 106 is formedon the first conductive layer 104. A deep trench 110 is formed in thedielectric layers 102 and 106. A second conductive layer 108 is formedover the second dielectric layer 106.

As may be seen in FIG. 1, the trench 110 bisects the first dielectriclayer 102 and the conductive layer 102 is located over sidewalls 120 ofthe first dielectric layer 102. The second conductive layer 108 islocated over sidewalls 122 of the second dielectric layer 106 and alsomay be in contact with the first conductive layer 104.

A semiconductor layer 130 may be fabricated over the second conductivelayer 108 and partially over the walls of the trench 110 that arecovered by the second conductive layer 108. A top electrode layer 140 isformed over the semiconductor layer 130. The electrode layer 140 isformed on the walls of the trench 110. The electrode layer 140 contactsthe second conductive layer 108 at certain points on the walls of thetrench 110 such as at contact points 150 a, 150 b, 150 c and 150 d inthis example.

In most of the cases, one of the dielectric layers 102 or 106 can beused as the deep trench 110. A deep opening is created by the trench 110so it causes a discontinuity in the semiconductor (or selecteddielectric) layer 130. For example, in top emission displays, one of thedielectric layers acts as a planarization layer which needs to be verythick as shown by the second dielectric layer 106. Thus, this layer is agood candidate for the deep trench structure. To create an even deepertrench, multiple stacked openings in the backplane can be used. Forexample, FIG. 1 shows a deep trench created in the backplane by usingtwo openings. To create the openings, different patterning techniquessuch lithography, liftoff, or molding, shadow masking and/or othertechniques can be used.

For depositing the dielectric, conductive and semiconductor layers,different techniques such as plasma enhanced chemical vapor deposition(PECVD), chemical vapor deposition (CVD), sputtering, vapor deposition,printing, spin coating, spray coating, and others can be used.

One example of developing a deep trench connection in a structure 100using multiple dielectric layers is shown in FIGS. 2A-2F as describedbelow. FIG. 2A shows the deposition of the dielectric layer 102. In thisexample, the dielectric layer 102 may be a material such asSilicon-Nitride which is deposited on top of existing structure on thebackplane. This may be one of the backplane dielectric layers or anextra layer. An opening 200 in the dielectric layer 102 in the positionof the eventual deep-trench 110 in FIG. 1 using photolithography. Theopening 200 is driven to depth of the backplane and therefore createssidewalls 202.

The conductive layer 104 is then deposited over the remaining dielectriclayer 102 as shown in FIG. 2B. The conductive layer 104 is depositedover the flat top surfaces of the dielectric layer 102 and the sidewalls202. The conductive layer 104 may be one of the backplane conductivelayers or an extra layer. In this example, the conductive layer 104 ispatterned as required by the design (a pattern should be left on top ofthe opening 200).

FIG. 2C shows the deposition of the second dielectric layer 106 over theconductive layer 104. The second dielectric layer 106 may be a polymerlayer deposited by spin (spray or printing) coating, or it may be astack of non-organic and polymer layers or non-organic only). This layercan be one of the layers required for the display structure such asplanarization layer, or it can be an extra layer added only for thetrench development. In this example, the second dielectric layer 106 isrelatively thick, thus allowing the creating of the deep trench 110. Thesecond dielectric layer 106 may be patterned using conventionalphotolithography (molding or other techniques can be used as well). Thepattern of the second dielectric layer 106 includes a second opening inthe position of the deep trench 110.

FIG. 2D shows the creation of a second opening 240 which is formedthrough patterning the second dielectric layer 106. The second opening240 allows sidewalls 242 to be formed in the second dielectric layer106. The second opening 240 allows the second dielectric layer 106 to beremoved so the conductive layer 104 is exposed. The second opening 240thus creates trench walls 122 shown in FIG. 1. The combination of thefirst opening 200 and the second opening 240 create the deep trench 110and corresponding side walls 120 and 122 in FIG. 1.

FIG. 2E shows the deposition of the second conductive layer 108 over thetrench created in the second dielectric layer 106. The second conductivelayer 108 may be one of the display conductive layers such as the OLEDanode layer or an extra layer added for the deep trench development. Theconductive layer 108 is patterned as required by the design of thedevice structure. The pattern of the conductive layer 108 includesleaving the conductive layer 108 on the first opening 200.

FIG. 2F shows the deposition of the semiconductor layer 130 on thesecond conductive layer 108. The semiconductor layer 130 may be an OLEDstructure or other thin film device structure. The semiconductor layer130 may be deposited with different techniques such as vapor deposition,printing, etc. Since the semiconductor layer 130 is very thin comparedto the depth of the trench 110 and the walls 122 of the trench aresteep, there will be a discontinuity such as the contact point 150 a inthe semiconductor layer 130 on the walls 122 and edge of the trench 110.

FIG. 2G shows the deposition of the top electrode 140. The top electrode140 connects to the second conductive layer 108 at the discontinuityareas of the semiconductor layer 130. FIG. 1 shows a number ofdiscontinuity areas 150 a, 150 b, 150 c and 150 d which allow contactbetween the top electrode 140 and the second conductive layer 108.

In the case of a deep trench, the semiconductor (or a dielectric) layer130 is discontinued at the edges (or walls of the trench). Therefore,after depositing the top electrode 140, the top electrode 140 isconnected to the conductive layers 108 at the walls of the trench 110.In this manner, a shadow mask may be avoided to create the contact sincethe semiconductor layer has discontinuities due to the trench thatallows contact.

FIG. 3 demonstrates a top view of a device 300 that includes topelectrodes 302, 304, 306 and 308. Each of the top electrodes arefabricated in the process described above. The top electrode 302includes an outer contact area 310 which corresponds to the trench wallsin FIG. 1. The outer contact area 310 is at the edge of the trenchstructure where there is a discontinuity of the semiconductor layer 130in FIG. 1. An inner contact area 320 also provides contact to theelectrode 108 at a discontinuity of the semiconductor layer 130 inFIG. 1. Thus, the top electrodes 302, 304, 306 and 308 are connected tothe conductive layers at the discontinuity areas of the semiconductorlayers in a trench 110.

When there are thin layers of semiconductor (dielectric) between twoconductive layers to form a device, a dielectric layer is used to coverthe edge of the bottom conductive layer. For example, an OLED canconsist of thin organic layers (with a total thickness of a few 100 nm)which are sandwiched between two conductive layers (at least one ofwhich is transparent). Since the thickness of the bottom conductivelayer is significantly more than that of the organic layers, to avoidany short, a dielectric is deposited on the bottom electrode and ispatterned in a way that covers the edge of the bottom electrode andleaves the center of the electrode exposed for organic layers.

In some cases, the resistance for one of the conductive layers(electrode) is high, causing a significant voltage drop in the case ofan array structure. For example, in the case of a top-emission OLED, thetop electrode is transparent and is made of very thin conductive layers.

In order to prevent a significant voltage drop, a lower resistanceconductive material may be used before depositing the semiconductorlayers. FIG. 4 shows a cross section of a device structure 400 thatavoids a significant voltage drop from resistance of one of theconductive layers. In this example, a substrate 402 supports adielectric layer 404 which serves as a backplane of the device structure400. The dielectric layer 404 may have numerous other layers that makeup the backplane of the device. A series of lower resistance conductivestrips 406 is formed on the dielectric layer 404. In this example, thelower resistance conductive strips 406 are patterned such that they havenumerous edges. A dielectric layer 408 is formed on some of theconductive strips 406. A thin semiconductor layer 410 which may be anorganic material is formed over the horizontal surfaces of the lowresistance conductive strips 406 and the dielectric layers 408. As maybe seen in FIG. 4, the edges of the lower resistance conductive strips406 remain exposed and not covered by the semiconductor layer. A topconductive layer 412 is then applied which in this example istransparent but has a high resistance. The top conductive layer 412 isin contact with the lower resistance conductive strips 406 on an edgesuch as on edges 414 thus shorting out the top conductive layer 412 andlowering the resistance of the contact.

The process of creating the structure in FIG. 4 is based on using lowerresistance conductive material for the conductive strips 406 beforedepositing the semiconductor (dielectric) layers. A low-resistanceconductive layer (or stack of conductive layers) is deposited which isthicker than the main semiconductor (dielectric) layers being depositedon top of it. This may be one of the conductive layers existing in thedevice or a new one added just for this reason. The low resistanceconductive layer is then patterned. The pattern should create moreedges. For example, stripes such as shown in FIGS. 4 and 5A or a meshshown in FIG. 5B may create numerous edges.

If there are other layers before the main semiconductor layer, theyshould be patterned after deposition to leave the edges exposed. Forexample, in FIG. 4, the dielectric layers 408 are patterned on the lowresistance conductive strips 406. The main semiconductor (dielectric)layer 410 is then deposited and patterned as needed by the design. Thehigh-resistance conductive layer 412 is then deposited and patterned asneeded. The pattern covers the low-resistance area of the conductivestrips 406 and, more importantly, at least one of its edges. Thefabrication of device is continued until all the other required layersafter this high-resistance conductive layer are deposited and patterned.

The edge or low-resistance conductive material cannot be covered by themain semiconductor (dielectric) since the thickness of the conductivelayer is greater than that of the main layer. The high-resistanceconductive layer will be shorted to the exposed edge of thelow-resistance conductive layer.

FIGS. 5A and 5B are top plan views of examples of the structure thatincorporates the low resistance conductive layers. FIG. 5A shows a topview of the device structure 400 in FIG. 4. The top conductive layer 412is a transparent layer with high resistance. Since the top conductivelayer 412 is deposited over the low resistance conductive strips 406, itcontacts the edges of the strips 406 and is shorted to prevent highresistance. The semiconductor layer 410 is fabricated over theconductive strips as well as other layers 408.

FIG. 5B is a top view of another device structure 500 that has the sametop conductive layer 412, semiconductor layer 410 and other layers 408as the structure 400 in FIG. 4. A low resistive conductive layer 450 ispatterned in a mesh structure. The low resistive conductive layer 450has a series of openings 452 that have multiple edges to create contactwith the high resistance top conductive layer 412 thus shorting the topconductive layer 412.

While particular embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationscan be apparent from the foregoing descriptions without departing fromthe spirit and scope of the invention as defined in the appended claims.

What is claimed is:
 1. A device structure providing contact toconductive layers via a deep trench structure, the device structurecomprising: a first dielectric layer including a flat top surface arounda first opening, the first opening having walls on the first dielectriclayer; a first conductive layer deposited over the flat top surface andthe first opening of the first dielectric layer; a second dielectriclayer deposited on the first conductive layer, the second dielectriclayer including a flat top surface around a second opening having wallson the second dielectric layer, wherein the first conductive layer islocated between the first and second dielectric layer; a secondconductive layer deposited over the second dielectric layer and thefirst and second openings; a semiconductor layer deposited on the secondconductive layer, the semiconductor layer being continuous on the flattop surface of the first and second dielectric layers, the semiconductorlayer continuously covering a lower portion of the walls of the firstand second openings, and being discontinuous on an upper portion of thewalls between the lower portion of the walls and the flat top surfaces;and a top electrode layer deposited on the semiconductor layer, the topelectrode layer in contact with the second conductive layer on the upperportion of the walls of the first or second openings.
 2. The devicestructure of claim 1, wherein the first and second openings are createdby one of lithography, liftoff, molding or shadow masking.
 3. The devicestructure of claim 1, wherein the semiconductor layer is an organiclight emitting diode.
 4. The device structure of claim 1, wherein thefirst dielectric layer is silicon-nitride and the second dielectriclayer is a polymer.
 5. The device structure of claim 1, wherein thefirst and second dielectric layers, the first and second conductivelayers and the semiconductor layer are deposited via at least one ofPECVD, CVD, sputtering, vapor deposition, printing, spin coating, andspray coating.
 6. A method of fabricating a device structure providingcontact to conductive layers via a deep trench structure, the methodcomprising: depositing a first dielectric layer having a flat topsurface; creating a first opening in the flat top surface of the firstdielectric layer, the first opening having walls on the first dielectriclayer; depositing a first conductive layer over the flat top surface andthe first opening of the first dielectric layer; depositing a seconddielectric layer having a flat top surface on the first conductivelayer; creating a second opening on the flat top surface of the seconddielectric layer, the second opening having walls on the seconddielectric layer, and wherein the first conductive layer is locatedbetween the first and second dielectric layers; depositing a secondconductive layer over the second dielectric layer and the first andsecond openings; depositing a semiconductor layer on the secondconductive layer, the semiconductor layer being continuous on the flattop surface of the first and second dielectric layers, the semiconductorlayer continuously covering a lower portion of the walls of the firstand second openings, and being discontinuous on an upper portion of thewalls between the lower portion of the walls and the flat top surfaces;and depositing a top electrode layer on the semiconductor layer, the topelectrode in contact with the second conductive layer on the upperportion of the walls of the first or second opening.
 7. The method ofclaim 6, wherein the first and second openings are created by one oflithography, liftoff, molding or shadow masking.
 8. The method of claim6, wherein the semiconductor layer is an organic light emitting diode.9. The method of claim 6, wherein the first dielectric layer issilicon-nitride and the second dielectric layer is a polymer.
 10. Themethod of claim 6, wherein the first and second dielectric layers, thefirst and second conductive layers and the semiconductor layer aredeposited via at least one of PECVD, CVD, sputtering, vapor deposition,printing, spin coating, and spray coating.
 11. A device structureproviding contact to conductive layers via a deep trench structure, thedevice structure comprising: a first dielectric layer including a topsurface and a side wall; a first conductive layer deposited over thefirst dielectric layer on the top surface and the side wall; a seconddielectric layer deposited on the first conductive layer, the seconddielectric layer including a top surface and a side wall; a secondconductive layer having a portion deposited over the top surface of thesecond dielectric layer and a portion deposited on the side wall of thesecond dielectric layer and the first conductive layer; a semiconductorlayer having a portion deposited on the portion of the second conductivelayer deposited over the top surface of the second dielectric layer, anda continuous portion deposited on the portion of the second conductivelayer deposited on a lower portion of the side wall of the seconddielectric layer and the first conductive layer, the semiconductor layerbeing discontinuous over the portion of the second conductive layerdeposited on an upper portion of the side wall between the lower portionof the side wall and the top surface; and a top electrode layerdeposited on the semiconductor layer, the top electrode layer in contactwith the second conductive layer on the upper portion deposited on theside wall of the second dielectric layer and the top electrode layerbeing in contact with the second conductive layer on the firstconductive layer on the upper portion of the side wall of the firstdielectric layer.
 12. The device structure of claim 11, wherein the sidewalls of the first and second dielectric layers are created by one oflithography, liftoff, molding or shadow masking.
 13. The devicestructure of claim 11, wherein the semiconductor layer is an organiclight emitting diode.
 14. The device structure of claim 11, wherein thefirst dielectric layer is silicon-nitride and the second dielectriclayer is a polymer.
 15. The device structure of claim 11, wherein thefirst and second dielectric layers, the first and second conductivelayers and the semiconductor layer are deposited via at least one ofPECVD, CVD, sputtering, vapor deposition, printing, spin coating, andspray coating.
 16. The device structure of claim 11, wherein the sidewalls of the first and second dielectric layers are positioned at apredetermined angle relative to the respective top surfaces.
 17. Thedevice structure of claim 11, wherein the first conductive layer is abackplane for the device structure.
 18. The device structure of claim11, wherein the second conductive layer is a low resistance conductorand the top electrode layer is a high resistance conductor.
 19. Thedevice structure of claim 11, wherein the top electrode layer istransparent.